Lubricant composition and method



United States Patent f 3,175,972 LUBRICANT CGMPOSITIGN AND METHQD BillMitacelr and John P. Graham, Bartlesville, Okla, assignors to PhillipsPetroleum Company, a corporation of Delaware No Drawing. Filed Mar. 6,1961, Ser. No.93,352 4 Claims. (Cl. 252-35) This invention relates toimproved high pressure fluid lubricants. In one aspect, this inventionrelates to lubricant compositions comprising a paraflinic base oil,extreme pressure lubricant additives, and a solid hydrocarbon polymer.In another aspect, this invention relates to a process for preparingimproved fluid lubricants which comprises the steps of heating aparatfinic base oil, dispersing therein a solid hydrocarbon polymer andsubsequently adding an extreme pressure lubricant additive.

It is known that extreme pressure additives can be added to petroleumbase stocks to produce gear oils. For ex ample, organic compoundscontaining sulfur, chlorine,

lead or phosphorus have proved to be useful, the decomposition productsof these compounds leading to the formation of high melting inorganiclubricant films on the metal surface. Among the types of compoundspreviously disclosed are compounds containing sulfur or compounds ofoxygen and sulfur, organic chlorine compounds (chlorinated wax), organicsulfur compounds (sulfurized fats, sulfurized olefins) and organiccompounds containing lead. Compositions consisting of one or more suchadditives have proved to be useful, for example, a mixture of metalnaphthenates, sulfurized hydrocarbons and chlorinated hydrocarbons, suchmixtures commonly referred to as SCL-type additives.

When extreme pressure lubricant additives are employed with parafiinicoils, the resulting compositions sometimes are unstable. For example,upon storage of oils containing these additives, sediments develop,forming at times an undesirably high amount of such sediment.

, Such an oil is unsatisfactory for obvious reasons; for example,storage stability is poor, valuable additive components precipitate out,and lubricating gears with such an oil could cause excessive wear orother damage due to settling of the precipitates during idle periods.

It is an object of this invention to provide an improved high pressurefluid lubricant composition which is stable in storage and use, and hasimproved lubricity. It is another object of this invention to provide aprocess for producing such an improved lubricant composition.

Other aspects, objects, and the several advantages of the invention areapparent from a study of this disclosure, and the appended claims.

According to our invention, improved extreme pressure lubricantcomposition is formed from a parailinic base oil, an extreme pressurelubricant additive, and anormally oil insoluble hydrocarbon polymer.Further according to our invention, improved lubricant may be formed comprising 50 to 99.4 weight percent of a paratfinic base oil, 0.5 to 45weight percent of extreme pressure lubricant additive, and 0.1 to 5weight percent of a hydrocarbon polymer. Further, according to ourinvention, the hydrocarbon polymer may be selected from solid polymersof ethylene and copolymers of ethylene with minor amounts ofcopolymerizable olefins. Polymers having a density between 0.900 and1.000 gram per cc. at 25 C. and more "ice especially those polymershaving a density between 0.940 and 1.000 gram per cc. at 25 C. are used.The 0.5 to 45 weight percent of extreme pressure lubricant additive maycomprise one or a blend of twoior more of the following: metalnaphthenates, phosphorized oils, sulfurized oils,phosphorized-sulfurized oils, and chlorinated hydrocarbons.

Further, according to our invention, there is provided an improvedprocess for producing extreme pressurefluid lubricants comprisingheating a paraffinic base oil, 'dispersing therein a normally oilsoluble hydrocarbon polymer, cooling and adding thereto an extremepressure additive. Also according to my invention, the paraflinic baseoil is heated to a temperature of at least 250 F. and preferably withinthe range between 325 and 450 F., the composition is cooled to atemperature below the cloud point to obtain uniform dispersion, and theextreme pressure lubricant additive is added at a temperature belowabout 200 F.

Thus, according to our invention, fluid lubricants which areparticularly suitable as gear oils are formulated so as to contain 50 to99.4 weight percent of a highly paraffinic base oil, .5 to 45 weightpercent of one or a blend of two or more extreme pressure additivesselected from polyvalent metal naphthenates, sulfurized hydrocarbons andchlorinated hydrocarbons, and 0.1 to 5 Weight percent of normallyoil-insoluble, highly dispersed hydrocarbon polymers, said polymerspreferably being the homopolymers and copolymers of ethylene having adensity within the range of 0.900 to 1.000. The incorporation of thepolymer permits utilization of paraffinic oils without attendantformation of sludge during storage and use.

In the preparation of lubricants, the use of parafiinic hydrocarbons isdesirable since, under oxidizing conditions, such hydrocarbons yieldpractically no sludge or oil-insoluble products. However, many extremepressure additives such as the SCL-type additives are not normallycompatible with paraffinic oils. We have discovered that thiscompatibility is greatly enhanced by incorporating in the lubricantcomposition a normally oil-insoluble polymer. The preferred polymers arethe polymers of ethylene and copolymers of ethylene and copolymerizableolefins. Extreme pressure additives which are stabilized byincorporation ofthe polymer in the composition comprise polyvalent metalnaphthenates, sulfurized hydrocarbons and chlorinated hydrocarbons asmore fully described below.

In accordancewith this invention lubricant compositions are preparedwith paraffinic base oils, polymer, and an extreme pressure additivewithin the following ranges.

Component: Weight percent Paraifinic base oil 50-99.4 Polymer 0.1-5Extreme pressure additive 0.5-

7 total lubricant composition, each being present in an amountsufiicient that the total of the three falls within the 0.5-45 weightpercent range specified above. In another embodiment, the extremepressure additive in the carbons from petroleum fractions are wellknown.

. -in US. 2,825,721.

g 6 above table comprises a phosphorized-sulfurized hydrocarboncontaining from 0.1 to 0.5 weight percent phosphorus and from 10 to 15weight percent sulfur. The amount of additive employed will be withinthe range given above for the components of the gear oil.

The paraflinic hydrocarbon oils employed as the base stocks areunrefined or refined products. Generally refined products are employedwhich are deasphalted and dewaxed, and which are solvent extracted toreduce the amount of aromatic hydrocarbons to a value below 10 percentby volume, preferably below percent by volume. Dewaxing may be carriedout by any conventional method, i.e., by solvent dewaxing using propaneor solvent mixtures, such as methyl ethyl ketone or methyl isobutylketone with benzene.

Selective solvents which remove the aromatic hydrosolvents can beemployed, when desired, to achieve base stocks of the desired highparafiinic content. Suitable selective solvents for aromatichydrocarbons include,

among others, the various phenols, sulfur dioxide, fur fural, and.fifi-dichlorodiethyl ether. v are commonly treated to remove residualtraces of solvent The raflinate oils and can be further refined, e.g.,clay treated and fractionated, to obtain base stocks of desiredviscosity grade. Some suitable processes have been reviewed by Nelson,Petroleum Refining Engineering, McGraw-Hill Book Company, New York(1958).

Such

, or higher molecular weight can be advantageously employed. Acids ofthe desired molecular weight range can be obtained by distillation ofthe crude, liberated acids. It is understood that the products compriseone or more acids. As is well known, the acids are oily liquids,volatile with steam, and boiling without appreciable decomposition inthe range of about 200 to 300 C. The most common acids are derivativesof cyclopentane, such as C H COOH, of cyclohexane, such as C H COOH, andof cycloheptane, such as C7H13COOH. Numerous other acids may be used. Byway of illustration, other suitable derivatives of cycloalkanes includecompounds having the The hydrocarbon polymers which stabilize theextreme U pressure components in the base oil are preferably the solidpolymers of ethylene and copolymers of ethylene with minor amounts ofcopolymerizable olefins. Co-

monomers which can be employed are preferably l-olefins having from 3 to8 carbon atoms and are'illustrated by the following: propylene,l-butene, l-pentene, l-hexene, l-octene, isobutylene, Z-methyl-l-buteneand 4-methyl-1- pentene. The preferred polymers are those having a denjsity between 0.940 and 1.000 g./cc. at 25 C. However,

polymers having a lower density, e.g., 0.900 to 0.940

g./cc. give useful results. The higher density products contribute notonly to lubricant stability but also greatly enhance the lubricity ofthe composition. Suitable meth- 'ods for preparing these preferredpolymers are described Other methods for preparing suitable polymersinclude the so-called organometallic processes, including such catalystsystems as a trialkylaluminum in conjunction with a transition metalcompound such as TiCl 1 v The preferred polymers, it should be noted,are not i normally soluble in the paraflinic base oils. By thisit ismeant that the polymers can only be dissolved in such oils byheating thepolymer. and oil mixture to. elevated temperatures, generally above250F. At lower temperatures, these solid polymers are substantiallyinsoluble.

, In the practice of this invention, the polymers are first dispersed ordissolved in the oil by heating, e.g., to a temperature of at least 250F. and preferably within the range between 325' and 450 F. The solutionis then cooled, with or without agitation, to a temperature below thecloud point to obtain a uniform dispersion. ,The extreme pressureadditive can be blended with the oil prior to, during or subsequent tomixing with the polymer. Preferably, however, additives other than thepolymer are mixed after thepolymer solution has been cooled to a 1temperature below about 200 F. so as to avoid decomposition orvolatilization of the additives.

By polyvalent, heavy metal salt of naphthenic acids is meant thecompounds formed by'neutralization of naphthenic acids with polyvalentmetal atoms having an atomic number of 28 or greater. Examples of metalsforming suitable salts include zinc, cadmium, barium, tin, lead, nickeland antimony. Of these, the lead salts are commonly preferred. By theterm naphthenic acids, it is meant the acid products derived fromkerosene and gas oil, other petroleum lubricating oil fractions andsimthe fatty acids.

structure where R is cyclopentyl, cyclohexyl and cycloheptyl, and x hasa value of 1 to 20.

These naphthenic acids can also be prepared by oxidation 'ofhydrocarbons. Hydrocarbons of the naphthenic type are oxidized by air attemperatures of 100 to 250 0, especially in the presence of catalysts,such as manganese salts and the organic acids then separated from theoil.

Processes for converting the acids to metal salts are similar to theWell-known processes for making soaps of The acids are mixed with acompound of a metal, preferably the carbonate, bicarbonate, the hydrousoxide or hydroxide, or the salt of a readily volatile acid, such as thesalts of hydrochloric acid or acetic acid and the mixture heated toeffect neutralization of the naphthenic acids and to remove volatileacids and water.

The sulfurized oils employed in the lubricant composition includesulfurized fatty oils, sulfurized hydrocarbon oils andphosphorized-sulfurized oils. Many such products are commerciallyavailable. These products cornmonly contain from 2 to about 15 weightpercent of sulfur. Illustrative methods for preparing suitable productsare described in US. 2,822,332 and US. 2,356,843.

The chlorinated hydrocarbons employed in the formulation of theseimproved lubricants are the products obtained Example I For theseexamples, a parafiinic base stock was prepared by mixing a commercial10-stock and a commercial 250-stock oil. These oils had been prepared bydistillation of a Mid-Continent crude oil to obtain a topped crude whichwas vacuum distilled to yield raw stocks of the desired viscosity grade.The raw stocks were solvent extracted with phenol, and the paraffinicrafiinate was separated and propane dewaxed. The properties for the 10-stock and 250-stock oils prepared by this process were as follows:

lo-stock 250stock Viscosity, SUS at 100 F Viscosity, SUS at 210 F.Viscosity index, Minimu Gravity, API Pour point, F Flash point, COO, FCarbon residue, Oonradson, Wt. percent The base stock was a blendcomprising 58.5% by weight of l-stock and 41.5% by weight of 250-stock.Using this base stock, two gear oils were prepared having the followingcomposition:

Weight Percent in- Control Gear Oil A Gear Oil B Base stock. AdPolyethylene Weight percent Lead naphthenate 20 Chlorinated hydrocarbon20-25 Sulfurized fish oil 55-60 The solid polyethylene has a density of0.960 g./cc. at 25 C. and a melt index of and was prepared by solutionpolymerization of ethylene over a chromium oxide containing catalyst asin US. 2,825,721.

Gear oil A was prepared by mixing the SCL additive blend with the oilwhich was heated to a temperature of 100 F. The components were mixedfor 15-20 minutes with vigorous agitation with a high speed mixer.

Gear oil B was similarly prepared except that the polymer was firstdissolved in the base stock. The oil was heated to about 350 F. and thepolymer added. Heating of the mixture was continued over about a 30minute period, during whichtime the temperature increased to about 400F. The solution was cooled to about 100 F., and the SCL additive blendincorporated as stated above for gear oil A.

Portions (about 400 ml.) of each of the above gear oils were stored inpint size bottles for a period of 3 /2 months. Periodic observationsshowed that gear oil B remained substantially unchanged and noprecipitation was apparent.

With gear oil A, sediments developed which formed a compact mass on thebottom of the container. After the 3 /2 month storage period, thesupernatant liquor was decanted and the weight of the settled portionwas found to be 11.3 weight percent of the gear oil. This represents anundesirably high amount of sediment.

Example 11 In a series of runs, a gear oil containing SCL additive andpolyethylene was compared with a commercial SCL gear oil. In these runs,SCL concentrate is identical to the SCL additive described in Example 1.In these runs, a modified dynamic corrosion test cell using a TimkenA-2037 cone and a Timken A-2126 cup was employed as the test bearingcell. The modification which was used was to support the base on a largeball thrust bearing. A dial indicator calibrated as a spring scale wasused to measure the force at the end of the torque arm extending fromthe test cell housing.

In each of the runs, the test bearing was submerged in the gear oil tobe tested. A 150-pound thrust load was applied and the speed was set at850 rpm. The test temperature was then controlled to the desired value.The results are expressed below in the form of a table.

1 Threshold for force indicator.

In the above table, gear oil X was an SAE commercial gear oil sold underthe trade name of Elco 28 gear oil. This gear oil contained 25 percentof SCL ooncentrate and 7.5 percent of a naphthenic-oontaiining basestock. Gear oil Y in the above table was prepared in the manner of gearoil B of Example I and contained 28.5 percent of SCL concentrate and 2percent of polyethylene, having a density of 0.960 gram per cc. and meltindex of 5 and prepared by solution polymerization of ethylene over achromium oxide containing catalyst as in US. 2,825,721, the remainderbeing paraifinic base stock. The values for relative friction are on anarbitrary scale but are on the same scale for both gear oils, the lowervalues being desirable.

Example III Two gear oils were formulated and tested in the followingmanner. In one gear oil formulation, a control formulation, parts byweight of a mixture containing 96 parts of an SAE-20 stock and 4 partsby weight of an SAE-250 stock were mixed with 435 parts by weight ofLubrizol Anglamol 81, a commercial extreme pressurephosphorized-sulfurized additive having a specific gravity at 60 F. of0.985 and an SUS viscosity at 210 F. of 140. The additive contains 12.6weight percent sulfur and 0.33 weight percent phosphorus. 0.2 part byweight per 100 parts base stock of a commercial pour point depressantsold under the trade name of Santopour C was added to the gear oilformulation. Santopour C is a commercial pour point depressant having aspecific gravity of 0.91 at 60 C., a viscosity of 460 SUS at 210 F., anda flash point of 300 F sold by Monsanto Chemical Co.

The other gear oil, representing gear oils of this invention, wasidentical to the above blend except that 3 parts by weight per 100 partsbase stock of a solid polyethylene was added to the formulation. Thepolyethylene used was identical to that employed in Example I and wasadded to the base stock by the method employed in Example I.

The two gear oils were then tested by Timken wear test. The conditionsused for the test were one hour at a load of 30 pounds. Details of theTimken E.P. tester and its operation are set forth in Proposed Method ofTesting for Measurement of Extreme Pressure Properties of Lubricants,A.S.T.M. Bulletin No. 228, pages 28-32, February 1958. For these tests,the so-called OK load procedure was followed, and the width of the scaron the steel test specimen was measured after a 10-minute test period bymeans of an optical micrometer.

The test block in the run using the gear oil containing no polyethylenehad a scar width of 0.052 inch. Under the same conditions, the testblock from the test using the gear oil containing polyethylene accordingto the method of this invention had a scar width of 0.030 inch. It canbe seen that considerably less wear result when the gear oils of thisinvention were employed.

In addition to the data given in the above example, tests were made in aFord Falcon to determine the steering torque with commercial gear oiland the gear oil of this invention. In a first test, the sector box wasfilled with SCL gear oil, a blend containing 28.5 percent SCL conthespecimen is suspended in the solution.

. per cc.

centrate as described in Example I, 3 percent of SCL concentratecommercial lubricating additive sold under the trade name of Elco No. 3,the remainder being base lubricant. The chassis of the Falcon in thistest was greased with factory fiilled grease. In a test at ambienttemperature (75-80 F.), the torque in inch pounds was 30.2, while at F.,the torque was 42.5 inch pounds. This represents an increase in steeringtorque of 40.7 percent in dropping the temperature from 75-80 to 0 F. Ina second test, the SCL gear oil was the same, and 2 percent ofthepolyethylene of the preceding example was added to the gear oil. In thisrun, the chassis was lubricated with a grease containing Phillipspolyethylene, as disclosed in our copending application Serial Number37,332, now Patent No. 3,112,270, filed June 20, 1960, by Bill Mitacekand John P. Graham. The torque at ambient temperature (75-80 F.) was28.4 inch pounds, and 33.7 inch pounds at 0 F. This represents anincrease in steering torque of only 18.6 percent. Thus,

a significant decrease in torque can be obtained by using thepolyethylene-containing lubricants.

Throughout this specification, in determining the polymer densitiesreferred to, the specimens are prepared by compression molding thepolymer at 340 F. until completely molten followed by cooling to 200 F.at a rate of about F. per minute. Water is then circulated through themold jacket to continue the cooling to 150 F. at a rate notexceeding F.per minute. The polymer is then removed from the mold and cooled to roomtemperature.

Density is determined by placing a smooth, void-free, pea-sized specimencut from a compression molded slab percent of an extreme pressureadditive selected from the group consisting of polyvalent metalnaphthenates, sulfurized hydrocarbons, chlorinated hydrocarbons andmixtures thereof, and 0.1 to 5 weight percent of a normallyoil-insoluble finely dispersed solid copolymer of ethylene and acopolymerizable olefin having 3-8 carbon atoms per molecule. a

2. An improved fluid lubricant comprising 50 to 99.4 weight percent of aparaffinic base oil, 0.5 to 45 weight percent of an extreme pressureadditive selected from the group cinsisting of polyvalent metalnaphthenates, sulfurized hydrocarbons, chlorinated hydrocarbons andmixtures thereof, and 0.1 to 5 weight percent of a normallyoil-insoluble finely dispersed solid polymer of ethylene.

of the polymer in a 50 ml. glass-stoppered graduate.

Carbon tetrachloride and methylcyclohexane are added to the graduatefrom burrettes in proportion such that During the addition of theliquids the graduate is shaken to secure thorough mixing. When themixture just suspends the specimen, a portion of the liquid istransferred to a small test tube and placed on the platform of aWestphal balance and the glass bob lowered therein. With the temperatureshown by the thermometer in the bob in the range 73-78 F., the balanceis adjusted until the pointer is at zero. The value shown in the scaleis taken as the specific gravity. With the balance standardized to read1.000 with a sample of distilled water at 4 C. the specific gravity willbe numerically equalto density in grams Melt index is determined bythemethod of A.S.T.M. Dl23S-57T except that five samples are taken andan average of these is determined.

Reasonable variation and modification are possible within the scope ofthe foregoing disclosure and the appended claims thereto, the essence ofwhich is an improved lubricant comprising a paraffinic base oil and anextreme pressure lubricant additive, stabilized by the addition of ahydrocarbon polymer and a process for producing an improved lubricantcomprising heating a parafiinic base oil, dispersing therein a normallyoil- 3. An improved fluid lubricant comprising 50 to 99.4 weight percentof a parafiinic base oil, 0.5 to 45 weight percent of an extremepressure additive selected from the group consisting of polyvalent metalnaphthenates, sulfurized hydrocarbons, chlorinated hydrocarbons andmixtures thereof, and 0.1 to 5 Weight percent of a polymer of ethylenehaving a density between 0.940 and 1.00 gram per cc. at 25 C.

4. An improved fluid lubricant comprising 50 to 99.4

.weight percent of a parafiinic base oil, 0.5 to 45 weight percent of anextreme pressure additive selected from the group consisting ofpolyvalent metal naphthenates, sulfurized hydrocarbons, chlorinatedhydrocarbons and mixtures thereof, and 0.1 to 5 weight percent of anormally oil-insoluble finely dispersed solid copolymer of ethylene anda l-olefin having 3 to 8 carbon atoms, said copolymer having a densitybetween 0.940 and 1.000 gram per cc. at 25 C.

References Cited by the Examiner UNITED STATES PATENTS 2,525,788 10/50Fontana et al 25259 2,692,257 10/54 Zletz 252-59 X 2,825,721 3/58 Hoganet al. 25259 3,060,120 10/ 62 Lippincott et al 252-59 X FOREIGN PATENTS767,002 1/57 Great Britain. 799,465 8/58 Great Britain.

OTHER REFERENCES I Lubrication, The Texas Company, N.Y., vol. 40, No. 6,June 1964 (page 74 relied on).

DANIEL E. WYMAN, Primary Examiner.

JOSEPH R. LIBERMAN, Examiner.

1. AN IMPROVED FLUID LUBRICANT COMPRISING 50 TO 99.4 WEIGHT PERCENT OF APARAFFINIC BASE OIL, 0.5 TO 45 WEIGHT PERCENT OF AN EXTREME PRESSUREADDITIVE SELECTED FROM THE GROUP CONSISTING OF POLYVALENT METALNAPHTHENATES, SULFURIZED HYDROCARBONS, CHLORINATED HYDROCARBONS ANDMIXTURES THEREOF, AND 0.1 TO 5 WEIGHT PERCENT OF A NORMALLYOIL-INSOLUBLE FINELY DISPERSED SOLID COPOLYMER OF ETHYLENE AND ACOPOLYMERIZABLE OLEFIN HAVING 3-8 CARBON ATOMS PER MOLECULE.